In order to make vehicles more fuel efficient, many manufacturers are implementing “Start/Stop” technology, where the engine is shut off when the vehicle comes to a stop and is restarted when acceleration is required. With the engine starting and stopping so frequently, reducing the occupant vibrations during these events is paramount.
The issue this disclosure is trying to solve is to control the high displacement vibrations generated during start-up and shut-down of ICE engines. This is an issue with most internal combustion engines, regardless of whether they are gas, diesel or hybrid (although some hybrids have a generator/motor that may reduce or prevent these vibrations).
Start-up is generally the bigger of the two issues, as the ignition cycle causes the powertrain to displace violently. The large displacement vibrations from this event cause noise and unwanted excitations in the passenger compartment. Shutdown typically does not create as high excitations (as it is not being driven by the combustion cycle), although shutdown can still create noise and unwanted excitations in the passenger compartment. When the ignition is shut off, the engine slows and RPMs drop, and as this occurs self-generated frequencies or engine orders excite low frequency rigid body modes in both the powertrain and chassis. This creates natural frequency oscillations which can intrude into the passenger compartment, disturbing the occupants.
Therefore a need exists for an inexpensive, reliable solution to address these oscillations.